1. Field of the Invention
The present invention relates in general to a fluid-filled elastic mount for flexibly connecting two members in a vibration damping or isolating fashion, and more particularly to such a fluid-filled elastic mount which has a simply constructed stopper device for limiting relative displacements between the two members when the mount receives an excessive amount of vibrational load, and which is therefore easy to manufacture.
2. Discussion of the Prior Art
Generally, an elastic mounting structure is disposed between two members of a vibration transmission system, for flexibly connecting the two members or for supporting one of the two members on the other fixed member, so that the elastic mounting structure can effectively damp and isolate input vibrations applied to the two members. As a type of the elastic mounting structure, there has been known a so-called fluid-filled elastic mount as disclosed in European Patent Applications EP-A No. 0 183 251 and 0 191 703. This fluid-filled elastic mount includes: (a) first and second support means which are spaced apart from each other in a load-receiving direction in which a vibrational load is applied to the elastic mount; (b) an elastic body interposed between the first and second support means, for elastic connection of the first and second support means; (c) a flexible closure member secured to the second support means and cooperating with at least the elastic body to define a fluid chamber filled with a non-compressible fluid; (d) partition means for dividing the fluid chamber into a pressure-receiving chamber formed on the side of the first support means, and an equilibrium chamber formed on the side of the second support means; (e) an orifice or restricted passage for restricted fluid communication between the pressure-receiving and equilibrium chambers; and (f) a hat-shaped member which is accomodated within the pressure-receiving chamber and fixedly supported by the first support means, such that the hat-shaped member extends in a direction perpendicular to the load-receiving direction.
In the known fluid-filled elastic mount constructed as described above, vibrations applied to the mount cause the non-compressible fluid to flow between the pressure-receiving and equilibrium chambers through the orifice, and to flow within the pressure-receiving chamber through a restricted portion defined between the hat-shaped member and an inner wall of the chamber. As a result, the input vibrations can be effectively damped or isolated, due to flows of the fluid and resonance of the fluid mass in the orifice and restricted portion, which are respectively tuned to specific frequency ranges.
The known fluid-filled elastic mount is usually provided with a stopper device for preventing an excessive amount of relative displacement between the first and second support means, so as to limit an amount of displacement between the above-indicated two members connected to the first and second support means, whereby an amount of deformation of the elastic body, upon application of an excessively large vibrational load to the mount.
An example of such a stopper device is disclosed in the above-identified EP-A publications. More specifically, the second support means is provided with abutting portions which respectively face opposite surfaces of the hat-shaped member in the load-receiving direction, such that the abutting portions of the second support means are normally spaced by a suitable distance apart from the opposite surfaces of the hat-shaped member. In this arrangement, the stopper device serves to limit the relative displacement between the second support means and the hat-shaped member (first support means) in opposite directions in which the vibrational load is applied, based on abutments of the hat-shaped member against the abutting portions. In this stopper device, a rubber layer having a suitable thickness is provided between each abutting portion of the second support means and the corresponding surface of the hat-shaped member, so as to serve as a buffer for absorbing or attenuating shocks upon abutting contacts of the abutting portions and the hat-shaped member.
In the thus constructed stopper device, however, the provision of the rubber layer between the facing surfaces of the hat-shaped member and second support means requires an independent or separate vulcanization process for applying a rubber material to the appropriate surfaces of the hat-shaped member and/or second support means, in addition to the vulcanization process in which a rubber block as the elastic body of the mount is secured to the first and second support means. The vulcanization process for the stopper device may be accomplished by applying a rubber material over the opposite surfaces of the hat-shaped member. However, it is still required to effect the vulcanization process to form the rubber block so as to connect the first and second support means. This results in increasing the number of process steps and cost of manufacture of the elastic mount, and lowering production efficiency. In this respect, it has been desired to provide a stopper device having a simpler construction than the conventional stopper device.